Just a point when using npm you can do two types of install. A local for the application you are writing and a global for use at the command line. The rule being … “Install locally for require(). Â Install globally for CLI apps.”
However and i completley missed this and so wasted an hour or so but when installing for a local app you need to run the command “npm install cluster” from the root of the app so it get put where the app can find it. Me i was assuming (dangerous) that you installed it to a central location and theat the $PATH pointed to it Doh!